Digital active phased array radar

ABSTRACT

In some examples, a radar system includes phase-locked loop (PLL) circuitry configured to generate a control voltage signal and processing circuitry configured to generate a reference signal to drive the PLL circuitry to generate the control voltage signal. In some examples, the radar system also includes voltage-controlled oscillator (VCO) circuitry configured to generate radio-frequency (RF) signals based on the control voltage signal and one or more antennas configured to transmit the RF signals and receive returned RF signals. In some examples, the radar system further includes receiver circuitry configured to generate intermediate-frequency (IF) signals based on the returned RF signals, wherein the processing circuitry is further configured to detect an object based on the IF signals.

This application claims the benefit of U.S. Provisional PatentApplication No. 62/571,604 (filed Oct. 12, 2017), which is incorporatedby reference herein.

TECHNICAL FIELD

This disclosure relates to radar.

BACKGROUND

Radar systems may be used by aircraft, ground installations or othervehicles to detect weather, aircraft or other objects in the surroundingspace. In smaller aircraft, such as some unmanned aerial vehicles(UAVs), weight, size, and power requirements may constrain the design ofthe radar system or preclude the use of a radar system altogether. Forexample, a small vehicle may include a battery power supply, so a radarsystem with high power consumption may rapidly deplete the energy storedin the battery.

SUMMARY

This disclosure describes a radar system configured to detect an objectbased on returned radio-frequency (RF) signals. The radar system mayinclude processing circuitry that is configured to drive phase-lockedloop (PLL) circuitry. The radar system may also includevoltage-controlled oscillator (VCO) circuitry configured to generate RFsignals based on a control voltage signal generated by the PLLcircuitry. The radar system may further include antennas configured totransmit and receive RF signals. Receiver circuitry may be configured togenerate intermediate-frequency (IF) signals based on the returned RFsignals.

In some examples, a radar system includes PLL circuitry configured togenerate a control voltage signal and processing circuitry configured togenerate a reference signal to drive the PLL circuitry to generate thecontrol voltage signal. The radar system also includes VCO circuitryconfigured to generate RF signals based on the control voltage signaland one or more antennas configured to transmit the RF signals andreceive returned RF signals. The radar system further includes receivercircuitry configured to generate IF signals based on the returned RFsignals, wherein the processing circuitry is further configured todetect an object based on the IF signals.

In some examples, a method includes driving, at processing circuitry,PLL circuitry to generate a control voltage signal and generating, atVCO circuitry, RF signals based on the control voltage signal. Themethod also includes transmitting, at one or more antennas, the RFsignals and receiving, at the one or more antennas, returned RF signals.The method further includes generating, at receiver circuitry, IFsignals based on the returned RF signals and detecting, at theprocessing circuitry, an object based on the IF signals.

In some examples, a radar system includes PLL circuitry configured togenerate a control voltage signal and processing circuitry configured todrive the PLL circuitry to generate the control voltage signal. Theradar system also includes VCO circuitry configured to generate RFsignals in a continuous wave mode based on the control voltage signaland one or more transmit antennas configured to transmit the RF signals.The radar system further includes a local oscillator (LO) configured togenerate an LO signal based on the RF signals, a coupler configured todeliver the RF signals to the one or more transmit antennas and to theLO, and four quadrants of receive antennas configured to receivereturned RF signals. The radar system includes four mixers configured togenerate IF signals based on the returned RF signals and based on the LOsignal, four IF amplifiers configured to filter the IF signals, and fouranalog-to-digital converters configured to generate digital signalsbased on the filtered IF signals, wherein the processing circuitry isfurther configured to detect an object based on the digital signals.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual block diagram depicting a radar system configuredto detect an object based on returned radio-frequency (RF) signals, inaccordance with some examples of this disclosure.

FIG. 2 is a conceptual block diagram depicting a radar system includingfour receive antennas configured to receive returned RF signals, inaccordance with some examples of this disclosure.

FIG. 3 is a conceptual block diagram depicting transmit antennas andreceive antennas separated by an electronic bandgap (EBG), in accordancewith some examples of this disclosure.

FIG. 4 depicts an example case for a radar system of this disclosure.

FIG. 5 depicts an example hardware configuration for a radar system ofthis disclosure.

FIGS. 6A and 6B depict multiple-beam Doppler techniques, in accordancewith some examples of this disclosure.

FIG. 7 shows a flowchart for example techniques for detecting an objectbased on returned RF signals, in accordance with some examples of thisdisclosure.

FIG. 8 is a conceptual block diagram depicting a system configured todetect an object and determine an estimated altitude, in accordance withsome examples of this disclosure.

FIG. 9 is a conceptual block diagram depicting three orientations for aradar device, in accordance with some examples of this disclosure.

FIG. 10 is a conceptual block diagram depicting five orientations for aradar device, in accordance with some examples of this disclosure.

FIG. 11 is a conceptual block diagram depicting a planetary gearset forpositioning a radar device, in accordance with some examples of thisdisclosure.

FIG. 12 is a conceptual block diagram depicting forward, altimeter, andaft pivot positions, in accordance with some examples of thisdisclosure.

DETAILED DESCRIPTION

This disclosure is directed to systems, devices, and methods for a radarsystem including processing circuitry configured to drive phase-lockedloop (PLL) circuitry to cause voltage-controlled oscillator (VCO)circuitry to generate RF signals for transmission. The radar system mayfurther include antennas configured to transmit and receive the RFsignals. The radar system may also include receiver circuitry that isconfigured to generate intermediate-frequency (IF) signals based on thereturned RF signals. The processing circuitry may be further configuredto detect objects based on the IF signals.

The radar system that may include fewer and/or simpler components thanexisting radar systems. The radar system may include common processingcircuitry for both transmission and receive functions. The radar systemmay include a small form factor, low mass, and low power consumption. Asa result, the radar system may be used in small vehicles, inexpensivevehicles, and/or mass-market vehicles. However, the techniques of thisdisclosure are applicable not only to small and/or low-cost radarsystems, but also to larger, heavier, and higher-cost radar systems.

To accommodate the small form factor, the radar system may be configuredto operate at higher frequencies, such as the K band between eighteenand twenty-seven gigahertz. Higher frequencies may translate intosmaller antenna(s) because of the shorter wavelengths. By operating inonly one frequency band, the radar system may include simpler circuitryand fewer components, as compared to existing radar systems that canoperate in two or more frequency band.

Land vehicles such as automobiles and unmanned aerial vehicles (UAV) maybenefit from sensors that assist with navigation and obstacle avoidance.A radar system of this disclosure may provide an independentsense-and-avoid (SAA) solution. The radar system may be useful inautomotive applications such as adaptive cruise control, obstaclemonitoring and avoidance, autonomous operation, and so on. Althoughother radar systems are available, a radar system of this disclosure mayhave a relatively small form factor and may meet low-cost targets formass production. A radar system of this disclosure, which may bereferred to as a digital active phased-array (DAPA) ultra lite radarsystem, may be used in consumer electronics and other mass marketdevices such as automobiles and small UAV's.

The autonomous automotive and UAV markets are growing exponentially. Theradar system described herein may be used in ultra-light applicationsand may fit those growing market needs. In addition to the hardwareinnovations described herein, the radar-system platform may also beconfigured to run SAA algorithms. The radar system may provide alow-cost software-defined radar system because objects are detected byprocessing circuitry based on returned RF signals. The radar system mayalso include develop and license tracking and sensor-fusion software. Insome examples, the radar system described herein may cost about twohundred and fifty dollars to produce. This radar system has multipleapplications for small unmanned vehicles on the ground, in the air, inspace, or in marine applications.

FIG. 1 is a conceptual block diagram depicting a radar system 100configured to detect an object 160 based on returned radio-frequency(RF) signals 145, in accordance with some examples of this disclosure.Radar system 100 may be configured to mount on a vehicle, such as anaerial vehicle, a land vehicle, or a marine vehicle. Radar system 100may be built on a single circuit board such as a printed circuit board(PCB). Antenna(s) 140 may be positioned on one side of the PCB, and theremaining components may be mounted on the other side of the PCB.

The total volume of radar system 100 may be approximately twelvecentimeters by approximately five centimeters by approximately onecentimeter. The total volume of radar system 100 may be approximatelythe size of a smartphone. The total power dissipation of radar system100 may be approximately ten watts during operation. The total mass ofradar system 100 may approximately one kilogram or less.

Processing circuitry 110 may be configured to generate reference signal115 to drive PLL circuitry to generate control voltage signal 125.Processing circuitry 110 may generate and deliver reference signal 115as a frequency chirp to PLL circuitry 120. Processing circuitry 110 maybe configured to generate reference signal 115 that is similar to theoutput of a direct digital synthesizer (DDS). Reference signal 115 maybe a linearly changing reference signal that PLL circuitry 120 receivesat the clock reference input of PLL circuitry 120. As compared to anexisting radar system with a DDS that drives a PLL, radar system 100 mayhave fewer components by not needing a specific DDS chip. In addition,an existing radar system may include other components that areassociated with the DDS chip. Radar system 100 may include a small formfactor because processing circuitry 110 can drive PLL circuitry 120 andprocess the return signals.

Processing circuitry 110 may also be configured to generate a variableclock signal for PLL circuitry 120 in order to set the frequency of RFsignals 135 through PLL circuitry 120 and VCO circuitry 130. Thus,processing circuitry 110 may operate similar to a direct digitalsynthesizer (DDS). In some examples, processing circuitry 110 mayinclude a multiprocessor system on a chip. Processing circuitry 110 maybe combination of a digital signal processor (DSP) with afield-programmable gate array (FPGA) fabric. One example of processingcircuitry 110 is the Zynq 7000 series made by Xilinx, Inc. of San Jose,Calif.

Processing circuitry 110 may be configured to receive IF signals 155from receiver circuitry 150. In some examples, radar system 100 mayinclude one or more analog-to-digital converters (ADC's) configured toconvert returned RF signals 145 or IF signals 155 to digital signals. Insome examples, the one or more ADC's may be integrated into processingcircuitry 110. Processing circuitry 110 may be configured to process thedigital signals to determine the location and/or velocity of object 160.Processing circuitry 110 may form beams based on the returned RF signals145 and IF signals 155.

Processing circuitry 110 may determine the location of object 160 basedon a beam focused on object 160. Processing circuitry 110 may usedigital-beam-forming techniques such as complex weighting based on phaseshifts and/or amplitude shifts. Processing circuitry 110 may beconfigured to determine a velocity of object 160 based on a shift in thefrequency of returned RF signals 145 from the frequency of RF signals135 (e.g., the Doppler frequency). Processing circuitry 110 may create athree-dimensional representation of the space around radar system 100.

Processing circuitry 110 may be configured to generate an output inresponse to detecting object 160. For example, processing circuitry 110may generate the output by generating an alert such as audio alert orvisual alert to the operator of the ownship vehicle. In some examples,processing circuitry 110 may cause the ownship vehicle to conduct anevasive maneuver, such as a braking maneuver, a stopping maneuver, alanding maneuver, a quick turn, and/or a change in direction in order toavoid a threat. Processing circuitry 110 may also be configured to storethe location and/or velocity of object 160 to a memory device.Processing circuitry 110, or a separate SAA system, may be configured totrack the position of object 160 over time. For example, processingcircuitry 110 may determine the velocity of object 160 relative to theownship vehicle in order to determine the imminence of a collisionbetween object 160 and the ownship vehicle.

PLL circuitry 120 may be configured to generate control voltage signal125 based on reference signal 115 and/or divided RF signal 132. PLLcircuitry 120 may be configured to generate control voltage signal 125in integer mode by multiplying the frequency of reference signal 115 andcomparing the frequency of the multiplied signal with the frequency ofdivided RF signal 132. PLL circuitry 120 may be configured to generatecontrol voltage signal 125 to drive the tuning circuit of VCO circuitry130. The output frequency of VCO circuitry 130 (e.g., RF signals 135)may be directly proportional to the amplitude of control voltage signal125. The relationship between the amplitude of control voltage signal125 and the frequency of RF signals 135 may be non-linear. Hence, aclosed-loop PLL circuitry 120 may achieve a desired exact operatingfrequency of RF signals 135 and the desired exact modulation. PLLcircuitry 120 may be configured to determine the swept bandwidth of RFsignals 135 and the time of the sweep using linear frequency-modulated(FM) modulation.

Control voltage signal 125 may cause VCO circuitry 130 to generate aK-band RF signal (e.g., RF signals 135) that is monitored and controlledby PLL circuitry 120. VCO circuitry 130 may be configured to provide asample of the output frequency divided by two (e.g., divided RF signal132), such that the 24-gigahertz (GHz) signal (e.g., RF signals 135) isreduced to 12 GHz (e.g., divided RF signal 132), so that PLL circuitry120 can receive divided RF signal 132 as a direct input. PLL circuitry120 may be configured to compare a reference clock signal fromprocessing circuitry 110 and divided RF signal 132 from VCO circuitry130 to determine control voltage signal 125. An example of PLL circuitry120 is the ADF41020 made by Analog Devices, Inc. of Norwood, Mass. PLLcircuitry 120 may be configured to cause VCO circuitry 130 to generateRF signals 135 as a continuous wave, such as a frequency-modulatedcontinuous wave (FMCW). In some examples, radar system 100 may beconfigured to operate in a continuous-wave mode and/or pulsed mode.

As stated above, processing circuitry 110 may be configured to generatereference signal 115 at a frequency that processing circuitry 110 canchange linearly over time. PLL circuitry 120 may be configured tomultiply the frequency of reference signal 115 by a fixed integer value,rather than operating in a fractional mode. Control voltage signal 125has a voltage amplitude that PLL circuitry 120 may deliver to VCOcircuitry 130 to achieve the desired final output frequency of RFsignals 135. VCO circuitry 130 may be configured to provide a sample ofthe output millimeter-wave (MMW) K-Band frequency (e.g., the frequencyof RF signals 135) that has a frequency that is half of the outputfrequency. For example, if the frequency of RF signals 135 is 24 GHz,VCO circuitry 130 may be configured to divide the frequency of RFsignals 135 by two to 12 GHz and send divided RF signal 132 to PLLcircuitry 120.

Thus, reference signal 115 may be a sinusoidal waveform, and processingcircuitry 110 can adjust the frequency of reference signal 115. PLLcircuitry 120 may be configured to generate control voltage signal 125as a voltage signal with an amplitude that is based on the frequency ofreference signal 115. PLL circuitry 120 may be configured to usefeedback from VCO circuitry 130 (e.g., divided RF signal 132) to compareto reference signal 115 from processing circuitry 110. PLL circuitry 120may be configured to multiply the frequency of reference signal 115 byan integer before comparing reference signal 115 to divided RF signal132.

For example, reference signal 115 may have a frequency of 128 MHz, andPLL circuitry 120 may be configured to multiply the frequency by 94 togenerate a multiplied signal at 12.032 GHz. If processing circuitry 110changes the frequency of reference signal 115 by just 1 MHz to 129 MHz,PLL circuitry 120 may generate a multiplied signal at 12.126 GHz, whichis a change of 94 MHz from 12.032 GHz. PLL circuitry 120 may beconfigured to compare this signal to divided RF signal 132 in order togenerate control voltage signal 125. As a result, a small change inclock frequency (e.g., of reference signal 115) may move the output(e.g., the amplitude of control voltage signal 125 and consequently thefrequency of RF signals 135) by a large amount.

Processing circuitry 110 may also be configured to generate a smalllinear chirp that PLL circuitry 120 multiplies in order to compare withdivided RF signal 132. VCO circuitry 130 may then be configured tocreate a chirp at approximately 24 GHz that sweeps a range of nearly 200MHz in some examples. It may be desirable to avoid using any fraction offrequency in PLL circuitry 120 because fractional mode may introducespurious frequencies (e.g., sideband frequencies). Therefore, it may bedesirable to use PLL circuitry 120 in integer mode and use other meanssuch as a DDS or processing circuitry 110 to provide linear frequencymodulation.

VCO circuitry 130 may be configured to generate RF signals 135 based oncontrol voltage signal 125. VCO circuitry 130 may be configured tomultiply the frequency of reference clock signal 111(from 110) to arriveat the frequency of RF signals 135. For example, PLL circuitry 120 maybe configured to multiply a reference clock signal (e.g., referencesignal 115) of 128 MHz may be multiplied by a factor of 94 to reach afinal output frequency of 12.032 GHz. The VCO output frequency (e.g., RFsignals 135) may be exactly two times the frequency of the multipliedsignal, or 24.064 GHz. VCO circuitry 130 may be configured to generateRF signals 135 in the K band of frequencies. VCO circuitry 130 may alsobe configured to generate a half-frequency output of RF signals 135. VCOcircuitry 130 may be configured to deliver the divide-by-two signal(e.g., divided RF signal 132) to PLL circuitry 120 in order to generatecontrol voltage signal 125. An example of VCO circuitry 130 is theHMC739 made by Analog Devices, Inc.

Antenna(s) 140 may be configured to transmit RF signals 135 and receivereturned RF signals 145. In some examples, antenna(s) 140 may include anarray of transmit antennas configured to transmit RF signals 135 as asingle beam. The transmit antennas may transmit RF signals 135 in acontinuous wave. Antenna(s) 140 may also include an array of receiveantennas configured to receive returned RF signals 145. Radar system 100may include a means for electrically isolating the transmit antennas andthe receive antennas, such as an electronic bandgap (EBG) isolator.

Antenna(s) 140 may include microstrip antenna(s) etched on a PCB.Antenna(s) 140 may be patch antenna(s) or discrete antenna(s). FIG. 3illustrates an example configuration of antenna(s) 140, where thereceive antennas are formed into four quadrants.

Receiver circuitry 150 may be configured to generate IF signals 155based on returned RF signals 145. Receiver circuitry 150 may include oneor more low-noise amplifiers (LNA's), mixers, IF amplifiers, and/or IFfilters. Receiver circuitry 150 may include operational amplifiers forprocessing returned RF signals 145. Receiver circuitry 150 may alsoinclude one or more ADC's configured to convert returned RF signals 145or IF signals 155 to digital signals for processing circuitry 110. Anexample of receiver circuitry 150 is the HMC1063, made by AnalogDevices, Inc. The HMC1063 includes a single mixer configured to outputquadrature I and Q IF signals 155, which may be useful in digital beamforming.

Object 160 may be any mobile object or remote object such as an aircraftsuch as a helicopter or a weather balloon, or object 160 may be a spacevehicle such as a satellite or spaceship. In yet other examples, object160 may include a land vehicle such as an automobile or a water vehiclesuch as a ship or a submarine. Object 160 may be a manned vehicle or anunmanned vehicle, such as a drone, a remote-control vehicle, a ballisticvehicle, or any suitable vehicle without any pilot or crew on board. Insome examples, object 160 may or may not be configured to transmitsurveillance signals, such as ADS-B, to inform the ownship vehicle(e.g., the vehicle carrying radar system 100) of the location anddirection of travel of object 160. Object 160 may also be a weatherballoon or an animal such as a bird. Object 160 may also be part ofterrain (e.g., ground or body of water), a stationary object (e.g., asign, a rock, or a tree), or a weather object (e.g., a water droplet).

In accordance with the techniques of this disclosure, the architectureof radar system 100 may be simpler and have fewer components thanexisting radar systems. The architecture may allow lower mass, cost,volume, and power consumption in some examples. In some examples, radarsystem 100 may include additional components for increasedfunctionality. For example, FIG. 2 depicts radar system 200 as anexample of a radar system with more components than radar system 100,such as memory device 212, coupler 232, and local oscillator (LO) 252.

Radar system 100 may have a lower cost than existing radar systemsbecause the components of radar system 100 can be used in other radarsystems. For example, receiver circuitry 150 may include similarcomponents as the circuitry of a larger or higher cost radar system.Thus, the design costs and component costs may be lower because ofvolume discounts and shorter design times.

FIG. 2 is a conceptual block diagram depicting a radar system 200including four receive antennas 240A-240D configured to receive returnedRF signals, in accordance with some examples of this disclosure. Radarsystem 200 is an example radar system with additional detail andcomponents, such as memory device 212, ethernet connection 214, and SAAsystem 216.

Memory device 212 may include volatile memory and/or non-volatilememory. Memory device 212 may be configured to store data such as objectcharacteristics. Memory device 212 may store locations and velocities ofobjects detected by processing circuitry 210. Processing circuitry 210may be configured to transmit information relating to the detectedobjects by ethernet connection 214 to SAA system 216.

SAA system 216 may determine whether a detected object poses a threat tothe ownship vehicle. SAA system 216, as known as detect-and-avoidsystem, may be further configured to cause the ownship vehicle to takean evasive maneuver if the detected object poses a threat. SAA system216 may be a separate processor that controls the movement of a vehicle,or SAA system 216 may be integrated into processing circuitry 210. Insome examples, radar system 200 may include a WiFi connection and/or aBluetooth connection between processing circuitry 210 and SAA system216. Processing circuitry 210 may use the WiFi connection or ethernetconnection 214 to connect to other electronics. Processing circuitry 210may use low-speed power over ethernet connection 214 on an edgeconnector to provide data and power

Crystal oscillator 222 may be configured to operate as a master clockfor radar system 200. For example, crystal oscillator 222 may deliver aone-hundred megahertz signal to PLL circuitry 224 and, in some examples,PLL circuitry 220. PLL circuitry 224 may be configured to increase theclock frequency for processing circuitry 210. Using a single masterclock for all of the components of radar system 200 may ensure coherencyfor the operation of the components. PLL circuitry 224 may be furtherconfigured to generate and deliver a clock signal for ADC's 258A and258C. In some examples, the frequency of the clock signal delivered toADC's 258A and 258C may be five megahertz.

Coupler 232 may be configured to deliver the RF signals to transmitantenna 240T and LO 252. Coupler 232 may be a microstrip coupler on thesurface of the PCB of radar system 200. LO 252 may be configured todeliver an LO signal to mixers 254A-254D of receiver circuitry 250 basedon the RF signals. In some examples, receiver circuitry 250 may beconfigured to operate as a homodyne receiver. As a homodyne receiver,receiver circuitry 250 may include simpler circuitry than asuper-heterodyne receiver.

Receive antennas 240A-240D may include four quadrants of receiveantennas configured to receive the returned RF signals and deliver thereturned RF signals to receiver circuitry 250. Receiver circuitry 250includes mixers 254A-254D and IF amplifiers 256A-256D, which may also beknown as IF filters. Each respective mixer and each respective IFamplifier may be part of a “channel” that delivers signals to processingcircuitry 210 in order to form up to four beams. Mixers 254A-254D may beconfigured to receive the returned RF signals and generate IF signalsbased on the returned RF signals and an LO signal received from LO 252.Mixers 254A-254D may down-convert the returned RF signals by subtractingthe LO frequency from the returned RF frequency.

Mixers 254A-254D may also generate an up-converted IF signal by addingthe frequencies of the returned RF signals and the LO signal, but IFamplifiers 256A-256D may be configured to filter out the frequenciesother than the down-converted frequency. IF amplifiers 256A-256D may beconfigured to filter the IF signals to produce filtered IF signals. Thefiltered IF signals may include the down-converted frequencies but notthe up-converted frequencies. IF amplifiers 256A-256D may also beconfigured to provide a range “pre-compensation” filter or a high-passfilter (HPF) that can provide gain as a function of the frequency of theIF signals. The gain of amplifiers 256A-256D may be equal to thepropagation losses in the particular application. For example, an HPFwith 12 dB per octave high-pass response from 1 kHz to 2 MHz may workwell for all detections of discrete targets. However, when radar system200 operates as a radar altimeter, the compensation could be adjusted tobe 6 dB per octave to match the expected range-squared variation inrange loss in altimeter mode.

Each of mixers 254A-254D may be configured to handle one of the fourreceive channels. Each of mixers 254A-254D may be an I-Q quadraturemixer. The outputs of mixers 254A-254D (e.g., IF signals) may bequadrature representations of the incoming signals from receive antennas240A-240D. Processing circuitry 210 may be configured to add together,or subtract, the quadrature outputs together with phase information.

ADC's 258A and 258C may be configured to convert analog signals such asthe IF signals or the filtered IF signals to digital signals forprocessing by processing circuitry 210. ADC's 258A and 258C may also beconfigured to receive a data conversion clock signal from PLL circuitry224 that may be designed to provide all clock and RF signals required inradar system 200 and provide fully coherent operation based on a singlemaster clock reference. For example, eighty megahertz as a serial clockdata conversion signal. An example of ADC's 258A and 258C are the DualADC AD7356 or Octal ADC Converter LTC9006 made by Analog Devices, Inc.The down-converted IF signals and the resulting digital signals may havea frequency that is low enough for processing circuitry 210 to processthe digital signals. In contrast, the returned RF signals may have afrequency of approximately twenty-four gigahertz. Thus, thedown-conversion process performed by receiver circuitry 250 may provideprocessing circuitry 210 with lower-frequency signals for easierprocessing.

Processing circuitry 210 may be configured to digitally andelectronically form beams that are a combination of two or more beams ortwo or more channels shown in FIG. 2. For example, processing circuitry210 may be configured to add two or more beams and/or subtract one ormore beams from other beams. Processing circuitry 210 and/or mixers254A-254D may be configured to form and move beams using addition andsubtraction for purposes such as looking straight out for air-to-airtargets, or straight down as an altimeter to locate a hill, a valley, astructure, or trees (e.g., for tree mapping). Processing circuitry 210may be configured to perform electronically scanning in a conical shapeor motion, a back and forth motion similar to windshield wipers, and/orany other motion or shape.

Radar system 200 may not include phase shifters or other hardware toform beams because processing circuitry 210 may electronically form andmove beams. Processing circuitry 210 may be configured to receivedigital signals from ADCs 258A and 258C that represent four independentquadrants. Processing circuitry 210 may be configured to sum ordifference the digital signals. Processing circuitry 210 may alsoperform complex weighting to create multiple beams and steer the receivepattern, to measure doppler to detect targets coming towards or movingaway from radar system 200. Processing circuitry 210 may also beconfigured to detect objects in azimuth and elevation. Processingcircuitry 210 may be configured to steer one or more receive beams viacomplex weights applied to four quadrants of I and Q channels generatedby mixers 254A-254D.

FIG. 3 is a conceptual block diagram depicting transmit antennas 340Tand receive antennas 340A-340D separated by an electronic bandgap (EBG)360, in accordance with some examples of this disclosure. As shown inFIG. 3, each of receive antennas 340A-340D may include four receiveantennas arranged in a substantially square format (e.g., within ten ortwenty degrees of an exactly square format). A substantially squareformat may include four antennas, where each antenna is within onecentimeter of a square format. Transmit antennas 340T and receiveantennas 340A-340D may take up most of the space on one side of a PCB,with the remaining components of the radar system mounted on the otherside of the PCB.

Transmit antennas 340T may be configured to transmit a wide beam of RFsignals. Alternatively, the transmit antennas may include just one patchantenna. In some examples, the transmitted beam may be approximatelyequal in azimuth and elevation. Processing circuitry may then beconfigured to form smaller beams on receive for detecting the locationof objects within those beams. The total field of regard in azimuth maybe forty-five degrees, and the total field of regard in elevation may beforty-five degrees.

EBG 360 may electrically isolate transmit antennas 340T from receiveantennas 340A-340D. As a result, EBG 360 may eliminate or reduce theinterference between transmit antennas 340T and receive antennas340A-340D. When transmit antennas 340T are transmitting RF signals, theRF signals may not significantly interfere with the reception ofreturned RF signals by receive antennas 340A-340D because of EBG 360.

FIG. 4 depicts an example case 400 for a radar system of thisdisclosure. Case 400 may be the size of a small mobile phone. Forexample, dimension 410 may be five-and-one-half inches or fourteencentimeters. In some examples, dimension 410 may be less than twentycentimeters. Dimension 412 may be two-and-one-half inches or sixcentimeters. In some examples, dimension 412 may be less than tencentimeters. Dimension 414 may be one-third of an inch or onecentimeter. In some examples, dimension 414 may be less than fivecentimeters. Case 400 may include printed plastic that is metalized forshielding inside. Case 400 may also include a one-eighth-inch powersupply jack on one edge, similar to a mobile phone.

FIG. 5 depicts an example hardware configuration for a radar system 500of this disclosure. FIG. 5 depicts a side view of radar system 500including housing 513, PCB 526, MIL circular connector 572, stand-off574, cavity 576, and heat sink 582. FIG. 5 depicts one exampleconstruction of radar systems 100 and 200. PCB 526, which are insidehousing 513, may include electrical connections for the components incavity 576 and the transmit antenna array and the receive antennaarray(s). PCB may include small metal shields that cover activecircuitry to prevent internal coupling and noise. The top side of PCB526 may include the antennas as microstrip, Substrate IntegratedWaveguide antennas, Slot antennas, or other printed antennas. The bottomside of PCB 526 may include the radio-frequency circuitry, the coredigital, and the power supply circuitry.

Housing 513 may cover most or all of radar system 500, such that thedimensions of housing 513 are approximately equal to the totaldimensions of radar system 500. MIL circular connector 572 may include amechanical element that is configured to mount on a vehicle frame.Stand-off 574 may be configured to protect the components in cavity 576from damage. Cavity 576 may be positioned in the center of the chassisof radar system 500. Cavity 576 may have a thickness of five or sixmillimeters. Heat sink 582 may include ribs machined into the chassis ofradar system 500. This system may also be packaged such that it can bedirectly integrated into an aircraft fuselage to provide weatherprotection or it may be carried externally on a small unmanned aerialsystem (e.g., a UAV).

FIGS. 6A and 6B depict multiple-beam Doppler techniques, in accordancewith some examples of this disclosure. FIG. 6A depicts the radar systemonboard vehicle 600A transmitting three beams 620A, 622A, and 624A atdifferent angles towards ground surface 640A. FIG. 6B depicts the radarsystem onboard vehicle 600A transmitting three beams 620B, 622B, 624B,and 626B at different angles towards ground surface 640B. Vehicles 600Aand 600B may be travelling in the x-axis direction with horizontalvelocities 610A and 610B while the radar system transmits RF signalstowards ground surface 640A or 640B. The radar systems onboard vehicles600A and 600B may be configured to determine altitudes 630A and 630B ofvehicles 600A and 600B above ground surfaces 640A and 640B.

The radar system may be used as an SAA device, a radar altimeter, and/ora velocimeter with options to allow it to become a navigation sensor bymeasuring Doppler in four quadrants (e.g., northeast, southeast,southwest, and northwest). The four quadrants may not represent theactual direction of travel relative to latitude and longitude. In otherwords, the northeast quadrant may not be northeast on a compass.Instead, the northeast quadrant may be defined as ahead of and to theright of vehicle 600A, e.g., in the positive x-axis direction and thepositive y-axis direction, and the southwest quadrant may be defined asbehind and to the left of vehicle 600A. For example, the radar systemmay form beams 620B, 622B, 624B, and 626B in four quadrants. Therefore,movement in the x-axis direction or the y-axis direction can be used tomeasure velocity in each direction, similar to a four-beam Dopplernavigator. The radar system may include simpler circuitry (e.g., fewercomponents) as compared to existing radar systems, so that the radarsystem of this disclosure may be a subset of a larger radar system.

The radar system may be configured to determine an estimated velocity ofvehicle 600A or 600B based on the Doppler shift of at least two receivebeams. The velocity of a vehicle may be correlated to the Doppler shiftat K-band frequencies in the direction of each of the four beams. Bymeasuring velocity in multiple directions, and starting from a knownposition (e.g., latitude and longitude), the radar system can determinethe velocity of the vehicle and an updated position of the vehicle.

For example, the radar system can keep track of the direction of travel,which may be based on the net vector result of all four Dopplermeasurements, and the net velocity of travel. The net velocity of travelmay be affected by wind, which may blow the system off course.Therefore, the radar system may determine the true position (e.g.,latitude and longitude) based on the direction of travel and the netvelocity of travel. This operation may be referred to as a “DopplerNavigator” mode. Doppler Navigator mode may be effective in dealing withGlobal Positioning System (GPS) jamming because the radar system canoperate in a GPS-denied mode of operation. A small unmanned vehicle thatis equipped with a “Doppler Navigator” mode may operate even when a GPSjammer impedes GPS navigation. The Doppler Navigator mode may work overwater or flat terrain where other methods of terrain mapping may not befeasible. Doppler Navigator can be combined with terrain mappingnavigation mode to provide verification of the accuracy of the DopplerNavigator. Doppler Navigator can be implemented in a three-beam mode, afour-beam mode, or with any other number of beams.

When operating as a Doppler Navigator, the radar system may beconfigured to use just two beams, but a configuration including three ormore beams is more viable for navigation. However, two or more beams inaltitude mode may be very useful for terrain navigation to determine anestimated altitude of nearby detailed features. The radar system maycombine terrain mode and/or altitude mode with Doppler Navigator mode.When the radar system combines Doppler Navigator mode with terrainmapping (with detailed digital beam forming) and altimeter operation,the radar system may be valuable to small unmanned vehicles. If thevehicle also includes a second radar system configured to operate as acollision avoidance system, the two radar systems may offer autonomousnavigation features including collision avoidance for full capability ona small unmanned vehicle.

The angles alpha a and theta 0 refer to angles relative to the directionof flight of vehicles 600A and 600B (e.g., the positive x-axisdireciton). The angle theta may be measured to the side of the aircraftflight path, which may be the positive x-axis direction. If horizontalvelocities 610A and 610B are pointing to the north, beams 620A and 620Bmay be in the northeast quadrant, beams 622A and 622B may be in thenorthwest quadrant, beams 624B may be in the southwest quadrant, beam626B may be in the southeast quadrant, and beam 624A may be directed inthe opposite direction of vehicle movement (e.g., the negative x-axisdirection).

The angle alpha may be the look-down angle from the vehicles 600A and600B, or the angle from each beam to ground surface 640A and 640B. Theradar system may be configured to determine the final doppler frequencybased on alpha, and the radar system may be further configured todetermine the direction of the doppler signal based on theta. As aresult, the northeast quadrant may be a front-right quadrant relative tothe aircraft nose. Beams 620A and 620B may allow the radar system tomeasure horizontal velocity 610A and 610B in the northeast direction.Beams 620A and 620B may allow the radar system to measure horizontalvelocity 610A and 610B in the northeast direction. Measuring velocitiesin all directions may permit the measurement of drift to the side ofvehicles 600A and 600B or even moving backwards, which may be possiblefor certain vehicles such as quadcopters. All of the beams include az-axis component, and the radar systems may use the beams to measurealtitudes 630A and 630B and/or vertical velocities 612A and 612B.

The radar systems of vehicles 600A and 600B may digitally form the beamsof FIGS. 6A and 6B on receive. The beams may be “squinted” due to theangle of the beams relative to the normal plane of the receive antennas.Four quadrants of receive antennas (quadrants 340A-340D shown in FIG. 3)are an example configuration of receive antennas that may form beams620B-626B. The radar system may use the beams to measure Doppler shiftdue to the relative velocities of the ground surface and other objects.The four receive subarrays of antennas may be arranged to include apurposeful skew in the theta and alpha directions to provide a desiredDoppler response in addition to a standard altimeter measurement.

The radar systems may also use the receive beams to determine locationsto the left, right, front or back of a specific altitude measurement.Determining locations and objects offset from directly vertical (e.g.,z-axis direction) allows a radar system to locate hills and otherobjects that the radar system can then index to a terrain map. The radarsystem may also be configured to navigate the vehicle. The radar systemmay be configured to receive azimuth scanning to map the terrainunderneath the vehicle (e.g., terrain-aided navigation). Terrain-aidednavigation includes mapping the ground surface underneath the vehicleand may use a stereo synthetic aperture radar (SAR) system.

In FIG. 6A, the processing circuitry may form beam 624A, which pointsaft from vehicle 600A, by combining two aft beams together in phase(see, e.g., beams 624B and 626B). The processing circuitry may beconfigured to leave the other two channels alone to operateindependently as they were such that beams 620A and 622A representindependent beams from a quadrant of receive antennas. The processingcircuitry may be configured to combine two of quadrants to form one beam(e.g., the beam 624A that is the back leg of the pattern. The processingcircuitry may be configured to perform any number of other possiblecombinations to create other resultant beams.

For example, the processing circuitry may combine all four beams into astandard monopulse beam, or combine the two left beams into a singleleft beam and combine the two right beams into a single right beam. Theprocessing circuitry may then be configured to subtract the single leftbeam and the single right beam to form an azimuth monopulse beam. Theprocessing circuitry may be further configured to form a single forwardbeam and a single aft beam and subtract the beams to form an elevationmonopulse beam. The processing circuitry may be configured to use thesingle monopulse beam (e.g., sum of all four) as a reference beam forthe monopulse differences.

In addition, the processing circuitry and/or the mixers may beconfigured to apply a complex weight to some or all of the four beams toproduce an I and Q output for each of the four beams. The processingcircuitry and/or the mixers may be configured to weight the I and Q's,i.e., multiply each signal by another I and/or Q value, and theprocessing circuitry may apply an independent I and Q weight to each ofthe four beams. The processing circuitry may be configured to controlthe weighting and summing of the beams to cause a net beam to point in adirection. The processing circuitry may be configured to performelectronic beam steering by weighting each of the four channels and thensumming the result of two or more channels. Therefore, the processingcircuitry may be configured to cause a resultant beam to point off tothe left, right, up, or down in order to steer the beam in anydirection. The radar system may be configured to create one big transmitbeam. On receive, the processing circuitry may apply complex weights toeach of four beams to steer each independent beam and/or resultant beamto the left, right, forward, or aft to make measurements or locateobject.

In some examples, the radar system may be configured to detect objectsin an object detection mode and to determine an estimated altitude ofthe vehicle in an altimeter mode. The radar system may be configured tointerleave the two modes or operate distinctly in each mode. The radarsystem may include a mechanical element to control the orientation ofthe antennas of the radar system. The mechanical element may beconfigured to position the antennas in a first orientation relative tothe vehicle to detect objects and in a second orientation relative tothe vehicle to determine an estimated altitude of the vehicle. Themechanical element may be configured to position the antennas in thesecond orientation by at least pointing the antennas at an angle that isapproximately parallel to a direction of movement of the vehicle. Themechanical element may be configured to position the antennas in thefirst orientation by at least pointing the antennas towards the groundsurface.

In some examples, the radar system may be a small, light-weight,high-resolution radar system. The radar system may include altimeterfunctionality by transmitting and/or receiving RF signals towards theground surface. The radar system may include a pivoting mechanismconfigured to pivot the radar system from looking forward (i.e.,horizontal or in the direction of travel of the vehicle) to lookingdownward. The pivoting mechanism may enable interleaving of SAA andaltimeter functions for simultaneous or near-simultaneous SAA andaltimeter functions. The pivoting mechanism may include a simple swivelor a gimbal mechanism.

The altimeter function may be useful in areas where high-resolutionradar altimeters are required (e.g., mountainous terrain, low-flyingvehicles, etc.). The altimeter function may be especially useful foraerial-photography UAV's, precision-terrain navigation for helicoptersor airplanes, trains in tunnels, and other vehicles. The altimeterfunction may be useful for aerial-photography UAV's that need tomaintain a specific altitude.

A commercial UAV may use a Global Navigation Satellite System (GNSS)(e.g., GPS) or an ultrasonic sensor for measurements of the height aboveground for the UAV. The GPS measurements may not be very accurate in allcircumstances. In addition, GPS may not operate properly indoors withoutline of sight to the satellites. Ultrasonic sensors may only be valid upto tenths of feet. The high-frequency radar system of this disclosuremay provide extremely accurate measurements at several hundreds of feetof range. The radar system may even switch waveforms to increase range.

A high-resolution radar system with modern semiconductor technology maybe small and light-weight. Given the possible small size of the radarsystem, a pivoting mechanism such as a gimbal, an A-track, planetarygears, and/or linear actuators may be configured to move the radarsystem from one position to another position. In some examples, thepivoting mechanism may be configured to move only the antennas and/orother components of the radar system. The radar system may be configuredto switch waveforms and range compensation filtering in the IF circuitryto optimize the two functions (e.g., SAA and altimeter). Forhigh-resolution and accuracy, the processing circuitry may be configuredto modify the waveforms.

The radar system may also be configured to modulate the radar waveformsto communicate with a base station (e.g., a ground control station) orother vehicles. When operating in altimeter mode, the radar system couldtransmit waveforms as a backup communication link with the base station.When operating in SAA mode, the radar system could modulate the radarwaveforms to communicate with other vehicles. The radar system may alsobe configured to provide additional SAA coverage by pivoting the radarsystem at large angles (e.g., one-hundred-and-eighty degrees) in theforward and aft directions. This pivoting may be especially useful forUAV's where distances may be relatively short because the pivotingmechanism can swing the radar system back and forth between positions.

FIG. 7 shows a flowchart for example techniques for detecting an objectbased on returned RF signals, in accordance with some examples of thisdisclosure. The techniques are described with reference to radar system100 of FIG. 1, although other components may perform similar techniques.

In the example of FIG. 7, processing circuitry 110 drives PLL circuitry120 to generate control voltage signal 125 (700). Processing circuitry110 may deliver a sinusoidal reference signal 115 to PLL circuitry 120to cause PLL circuitry 120 to generate control voltage signal 125. PLLcircuitry 120 may also be configured to generate control voltage signal125 based on divided RF signal 132, which may be a waveform at one-halfof the frequency of RF signals 135. In the example of FIG. 7, VCOcircuitry 130 generates RF signals 135 based on control voltage signal125 (702). RF signals 135 may have a frequency in the K or Ka band(i.e., from eighteen gigahertz to twenty-seven gigahertz or from 27 GHzto 40 GHz).

In the example of FIG. 7, antenna(s) 140 transmit RF signals 135 (704).In the example of FIG. 7, antenna(s) 140 receive returned RF signals 145(706). The receive antennas and transmit antennas may be separated by anEBG that provides electrical isolation. The high frequencies of RFsignals 135 and 145 may allow relatively small antenna. For example, attwenty-four gigahertz, a half-wavelength antenna is six or sevenmillimeters long. Thus, relatively high frequencies may allow smallerantennas and a smaller overall size for radar system 100.

In the example of FIG. 7, receiver circuitry 150 generates IF signals155 based on returned RF signals 145 (708). Receiver circuitry 150 maybe configured to down-convert returned RF signals 145 by subtracting thefrequency of returned RF signals 145 from an LO signal that is based onthe frequency of RF signals 135. In the example of FIG. 7, processingcircuitry 110 detects object 160 based on IF signals 155 (710). Radarsystem 100 may include one or more ADC's configured to convert IFsignals 155 to digital signals for processing.

FIG. 8 is a conceptual block diagram depicting a system 800 configuredto detect an object 870 and determine an estimated altitude, inaccordance with some examples of this disclosure. In some examples,phased-array radar device 820 may include radar system 100, butphased-array radar device 820 may also include other radar systems. Forexample, phased-array radar device 820 may include any activeelectronically scanned array radar device or any passive electronicallyscanned array radar device.

FIG. 9 is a conceptual block diagram depicting three orientations930A-930C for a radar device 920, in accordance with some examples ofthis disclosure. Track 940 may be configured to position radar device920 in orientation 930A to detect objects. When in orientation 930A,radar device 920 may be pointed at an angle that is approximatelyparallel to a direction of movement of airframe 900. Airframe 900 may bepart of a vehicle. When in orientation 930A, radar device 920 may alsobe pointed at an angle that is approximately parallel to the groundsurface.

Track 940 may be configured to position radar device 920 in orientation930C to determine an estimated altitude of airframe 900. When inorientation 930C, radar device 920 may be pointed at an angle towards aground surface. When in orientation 930B, radar device 920 may be ableto detect objects and determine an estimated altitude of airframe 900.

FIG. 10 is a conceptual block diagram depicting five orientations for aradar device, in accordance with some examples of this disclosure. Track1040 may be configured to position radar device 1020 in a forwardorientation 1030A, an aft orientation 1030E, a downward orientation1030C, or intermediate orientations 1030B and 1030D.

FIG. 11 is a conceptual block diagram depicting a planetary gearset forpositioning a radar device 1120, in accordance with some examples ofthis disclosure. Outer planetary gear 1116 may be configured to controlthe orientation of radar device 1120. Inner planetary gear 1114 may beconfigured to rotate inside outer planetary gear 1116. Stationary gear1112 may be configured to cause outer planetary gear 1116 to rotate. Astationary motor may be configured to drive stationary gear 1112 tocause the rotation of planetary gear 1116. The planetary gearset of FIG.11 and the track devices of FIGS. 9 and 10 are examples of mechanicalelements that may be configured to position a radar system in differentorientations.

FIG. 12 is a conceptual block diagram depicting forward, altimeter, andaft pivot positions, in accordance with some examples of thisdisclosure. A mechanical element may be configured to pivot the radarsystem in three or more different positions so that the radar system candetect obstacles and determine an estimated altitude.

The techniques of this disclosure may be implemented in a device orarticle of manufacture including a computer-readable storage medium. Theterm “processing circuitry,” as used herein may refer to any of theforegoing structure or any other structure suitable for processingprogram code and/or data or otherwise implementing the techniquesdescribed herein. Elements of processing circuitry 110 and/or 210 may beimplemented in any of a variety of types of solid state circuitelements, such as CPUs, CPU cores, GPUs, digital signal processors(DSPs), application-specific integrated circuits (ASICs), a mixed-signalintegrated circuits, field programmable gate arrays (FPGAs),microcontrollers, programmable logic controllers (PLCs), programmablelogic device (PLDs), complex PLDs (CPLDs), a system on a chip (SoC), anysubsection of any of the above, an interconnected or distributedcombination of any of the above, or any other integrated or discretelogic circuitry, or any other type of component or one or morecomponents capable of being configured in accordance with any of theexamples disclosed herein.

The radar systems of FIGS. 1-6B may include one or more memory devicesthat include any volatile or non-volatile media, such as a RAM, ROM,non-volatile RAM (NVRAM), electrically erasable programmable ROM(EEPROM), flash memory, and the like. The one or more memory devices maystore computer readable instructions that, when executed by processingcircuitry 110 or 210, cause the processing circuitry to implement thetechniques attributed herein to processing circuitry.

Elements of processing circuitry 110 and/or 210 may be programmed withvarious forms of software. The processing circuitry 110 and/or 210 maybe implemented at least in part as, or include, one or more executableapplications, application modules, libraries, classes, methods, objects,routines, subroutines, firmware, and/or embedded code, for example.Elements of the processing circuitry 110 and/or 210 as in any of theexamples herein may be implemented as a device, a system, an apparatus,and may embody or implement a method of receiving surveillance signalsand predicting future vehicle maneuvers.

The techniques of this disclosure may be implemented in a wide varietyof computing devices. Any components, modules or units have beendescribed to emphasize functional aspects and does not necessarilyrequire realization by different hardware units. The techniquesdescribed herein may be implemented in hardware, software, firmware, orany combination thereof. Any features described as modules, units orcomponents may be implemented together in an integrated logic device orseparately as discrete but interoperable logic devices. In some cases,various features may be implemented as an integrated circuit device,such as an integrated circuit chip or chipset.

A “vehicle” may be an aircraft, a land vehicle such as an automobile, ora water vehicle such as a ship or a submarine. An “aircraft” asdescribed and claimed herein may include any fixed-wing or rotary-wingaircraft, airship (e.g., dirigible or blimp buoyed by helium or otherlighter-than-air gas), suborbital spaceplane, spacecraft, expendable orreusable launch vehicle or launch vehicle stage, or other type of flyingdevice. An “aircraft” as described and claimed herein may include anycrewed or uncrewed craft (e.g., uncrewed aerial vehicle (UAV), flyingrobot, a ballistic vehicle, or automated cargo or parcel delivery droneor other craft).

The following numbered examples demonstrate one or more aspects of thedisclosure.

EXAMPLE 1

A radar system includes PLL circuitry configured to generate a controlvoltage signal and processing circuitry configured to generate areference signal to drive the PLL circuitry to generate the controlvoltage signal. The radar system also includes VCO circuitry configuredto generate RF signals based on the control voltage signal and one ormore antennas configured to transmit the RF signals and receive returnedRF signals. The radar system further includes receiver circuitryconfigured to generate IF signals based on the returned RF signals,wherein the processing circuitry is further configured to detect anobject based on the IF signals.

EXAMPLE 2

The radar system of example 1, further including a panel including theone or more antennas, wherein the one or more antennas include one ormore transmit antennas configured to transmit the RF signals and fourquadrants of receive antennas, wherein each quadrant of the fourquadrants includes at least four receive antennas arranged in asubstantially square format. The receive antennas are configured toreceive the returned RF signals and deliver the returned RF signals tothe receiver circuitry.

EXAMPLE 3

The radar system of examples 1-2 or any combination thereof, furtherincluding a case enclosing the PLL circuitry, the VCO circuitry, the oneor more antennas, the receiver circuitry, and the processing circuitry,wherein a longest dimension of the case is less than twenty centimeters,and wherein a second-longest dimension of the case is less than tencentimeters.

EXAMPLE 4

The radar system of examples 1-3 or any combination thereof, furtherincluding an analog-to-digital converter configured to generate digitalsignals based on the IF signals, wherein the processing circuitry isconfigured to detect the object based on the digital signals.

EXAMPLE 5

The radar system of examples 1-4 or any combination thereof, wherein theradar system is configured to operate in only one frequency band.

EXAMPLE 6

The radar system of examples 1-5 or any combination thereof, furtherincluding an LO and a coupler configured to deliver the RF signals to atransmit antenna and deliver the RF signals to the LO, wherein the LO isconfigured to deliver an LO signal to the receiver circuitry based onthe RF signals.

EXAMPLE 7

The radar system of examples 1-6 or any combination thereof, furtherincluding a PCB, wherein the PLL circuitry, the processing circuitry,the VCO circuitry, and the receiver circuitry are mounted on the PCB.The radar system also includes an LO mounted on the PCB and configuredto generate an LO signal and deliver the LO signal to the receivercircuitry. The radar system further includes a coupler on the PCBconfigured to couple the RF signals to the LO, wherein the LO isconfigured to generate the LO signal based on the coupled RF signals.

EXAMPLE 8

The radar system of examples 1-7 or any combination thereof, wherein thereceiver circuitry includes a mixer configured to generate two IFsignals based on the returned RF signals and a local oscillator signal.The receiver circuitry also includes two IF amplifiers configured tofilter the two IF signals into filtered IF signals and ananalog-to-digital converter configured to generate digital signals basedon the filtered IF signals, wherein the processing circuitry isconfigured to detect the object based on the digital signals.

EXAMPLE 9

The radar system of examples 1-8 or any combination thereof, wherein theprocessing circuitry is configured to drive the PLL circuitry to operatein a continuous wave mode.

EXAMPLE 10

The radar system of examples 1-9 or any combination thereof, wherein theprocessing circuitry is configured to detect a velocity of the objectbased on the IF signals.

EXAMPLE 11

The radar system of examples 1-10 or any combination thereof, furtherincluding a crystal oscillator configured to operate as a master clockfor the processing circuitry and the PLL circuitry.

EXAMPLE 12

The radar system of examples 1-11 or any combination thereof, whereinthe VCO circuitry is further configured to generate a divided RF signal,and wherein the PLL circuitry is further configured to generate amultiplied signal by multiplying a frequency of the reference signal andcompare the multiplied signal and the divided RF signal. The PLLcircuitry is configured to generate the control voltage signal based oncomparing the multiplied signal and the divided RF signal.

EXAMPLE 13

The radar system of examples 1-12 or any combination thereof, whereinthe radar system is configured to mount on a vehicle, and wherein theprocessing circuitry is further configured to determine an estimatedaltitude of the vehicle based on the IF signals.

EXAMPLE 14

The radar system of examples 1-13 or any combination thereof, whereinthe radar system is configured to mount on a vehicle, and wherein theprocessing circuitry is further configured to determine at least tworeceive beams of returned RF signals and measure Doppler shift of the atleast two receive beams, wherein the processing circuitry is configuredto determine an estimated velocity of the vehicle based on the Dopplershift of the at least two receive beams.

EXAMPLE 15

A method includes driving, at processing circuitry, PLL circuitry togenerate a control voltage signal and generating, at VCO circuitry, RFsignals based on the control voltage signal. The method also includestransmitting, at one or more antennas, the RF signals and receiving, atthe one or more antennas, returned RF signals. The method furtherincludes generating, at receiver circuitry, IF signals based on thereturned RF signals and detecting, at the processing circuitry, anobject based on the IF signals.

EXAMPLE 16

The method of example 15, wherein receiving the returned RF signalsincludes receiving, at four quadrants of receive antennas, the returnedRF signals, wherein generating IF signals includes generating, at fourmixers, the IF signals, wherein the method further includes filtering,at four IF amplifiers, IF signals into filtered IF signals, and whereindetecting the object is further based on the filtered IF signals.

EXAMPLE 17

The method of examples 15-16 or any combination thereof, furtherincluding generating, at an analog-to-digital converter, digital signalsbased on the IF signals, wherein detecting the object is further basedon the digital signals.

EXAMPLE 18

The method of examples 15-17 or any combination thereof, furtherincluding generating, at an analog-to-digital converter, digital signalsbased on the IF signals, wherein detecting the object is further basedon the digital signals.

EXAMPLE 19

The method of examples 15-18 or any combination thereof, whereintransmitting the RF signals includes transmitting, at the one or moreantennas, the RF signals in only one frequency band.

EXAMPLE 20

The method of examples 15-19 or any combination thereof, furtherincluding delivering, by a coupler, the RF signals to the one or moreantennas; delivering, by the coupler, the RF signals to an LO; anddelivering, by the LO, an LO signal to the receiver circuitry based onthe RF signals.

EXAMPLE 21

The method of examples 15-20 or any combination thereof, whereingenerating the RF signals includes generating, at the VCO circuitry, theRF signals in a continuous wave mode.

EXAMPLE 22

A radar system includes PLL circuitry configured to generate a controlvoltage signal and processing circuitry configured to drive the PLLcircuitry to generate the control voltage signal. The radar system alsoincludes VCO circuitry configured to generate RF signals in a continuouswave mode based on the control voltage signal and one or more transmitantennas configured to transmit the RF signals. The radar system furtherincludes an LO configured to generate an LO signal based on the RFsignals, a coupler configured to deliver the RF signals to the one ormore transmit antennas and to the LO, and four quadrants of receiveantennas configured to receive returned RF signals. The radar systemincludes four mixers configured to generate IF signals based on thereturned RF signals and based on the LO signal, four IF amplifiersconfigured to filter the IF signals, and four analog-to-digitalconverters configured to generate digital signals based on the filteredIF signals, wherein the processing circuitry is further configured todetect an object based on the digital signals.

EXAMPLE 23

The radar system of example 22, further including a memory device,wherein the processing circuitry is configured to detect the object byat least determining a location of the object based on the returned RFsignals and determining a velocity of the object based on the returnedRF signals. The processing circuitry is further configured to store thelocation of the object to the memory device and store the velocity ofthe object to the memory device.

EXAMPLE 24

A system is configured to be mounted on a vehicle, the system includingone or more phased-array radar devices configured to transmit firstradar signals, receive first returned radar signals, transmit secondradar signals, and receive second returned radar signals. The systemalso includes processing circuitry configured to detect an object basedon the first returned radar signals and determine an estimated altitudeof the vehicle above a ground surface based on the second returned radarsignals.

EXAMPLE 25

The radar system of example 24, wherein the one or more phased-arrayradar devices includes a single phased-array radar device, and thesystem further includes a mechanical element configured to position thesingle phased-array radar device in a first orientation relative to thevehicle and position the single phased-array radar device in a secondorientation relative to the vehicle. The single phased-array radardevice is configured to transmit the first radar signals while thesingle phased-array radar device is positioned in the first orientation,receive the first returned radar signals while the single phased-arrayradar device is positioned in the first orientation, transmit the secondradar signals while the single phased-array radar device is positionedin the second orientation, and receive the second returned radar signalswhile the single phased-array radar device is positioned in the firstorientation.

EXAMPLE 26

The method of examples 24-25 or any combination thereof, wherein themechanical element is configured to position the single phased-arrayradar device in the first orientation by at least pointing the antennaarray of the single phased-array radar device at an angle that isapproximately parallel to a direction of movement of the vehicle. Themechanical element is configured to position the single phased-arrayradar device in the second orientation by at least pointing an antennaarray of the single phased-array radar device towards the groundsurface.

EXAMPLE 27

The method of examples 24-26 or any combination thereof, wherein themechanical element is further configured to position the singlephased-array radar device in a third orientation by at least pointingthe antenna array of the single phased-array radar device at an anglethat is approximately parallel to a direction of movement of the vehicleand pointing in an opposite direction of the first orientation. Thesingle phased-array radar device is configured to transmit the firstradar signals while the single phased-array radar device is positionedin the third orientation and receive the first returned radar signalswhile the single phased-array radar device is positioned in the thirdorientation.

EXAMPLE 28

The method of examples 24-27 or any combination thereof, wherein themechanical element is further configured to position the singlephased-array radar device in an intermediate orientation by at leastpointing the antenna array of the single phased-array radar device at anangle that is between the first orientation and the second orientation.

EXAMPLE 29

The method of examples 24-28 or any combination thereof, wherein themechanical element includes a planetary gearset including an outerplanetary gear configured to control an orientation of the singlephased-array radar device, an inner planetary gear configured to rotateinside the outer planetary gear, and a stationary motor and stationarygear configured to cause the outer planetary gear to rotate.

EXAMPLE 30

The method of examples 24-29 or any combination thereof, wherein the oneor more phased-array radar devices includes a first phased-array radardevice and a second phased-array radar device. The first phased-arrayradar device includes an antenna array pointed approximately parallel toa direction of movement of the vehicle and configured to transmit thefirst radar signals and receive the first returned radar signals. Thesecond phased-array radar device includes an antenna array pointedtowards the ground surface and configured to transmit the second radarsignals and receive the second returned radar signals.

EXAMPLE 31

The method of examples 24-30 or any combination thereof, wherein theprocessing circuitry is further configured to determine at least tworeceive beams on receive towards the ground surface based on thereturned signals and determine a distance to the ground surface based onthe at least two receive beams.

EXAMPLE 32

The method of examples 24-31 or any combination thereof, wherein theprocessing circuitry is further configured to measure Doppler shift ofthe at least two receive beams, and wherein the processing circuitry isconfigured to determine an estimated velocity of the vehicle based onthe Doppler shift of the at least two receive beams.

EXAMPLE 33

The method of examples 24-31 or any combination thereof, wherein theprocessing circuitry is further configured to determine at least fourreceive beams towards the ground surface based on the returned signalsand determine a distance to the ground surface based on the at leastfour receive beams.

Various illustrative aspects of the disclosure are described above.These and other aspects are within the scope of the following claims.

What is claimed is:
 1. A radar system comprising: phase-locked loop(PLL) circuitry configured to generate a control voltage signal;processing circuitry configured to generate a reference signal to drivethe PLL circuitry to generate the control voltage signal;voltage-controlled oscillator (VCO) circuitry configured to generateradio-frequency (RF) signals based on the control voltage signal; one ormore antennas configured to: transmit the RF signals; and receivereturned RF signals; and receiver circuitry configured to generateintermediate-frequency (IF) signals based on the returned RF signals,wherein the processing circuitry is further configured to detect anobject based on the IF signals.
 2. The radar system of claim 1, furthercomprising a panel including the one or more antennas, wherein the oneor more antennas comprise: one or more transmit antennas configured totransmit the RF signals; and four quadrants of receive antennas, andwherein each quadrant of the four quadrants includes at least fourreceive antennas arranged in a substantially square format, and whereinthe receive antennas are configured to: receive the returned RF signals;and deliver the returned RF signals to the receiver circuitry.
 3. Theradar system of claim 1, further comprising a case enclosing the PLLcircuitry, the VCO circuitry, the one or more antennas, the receivercircuitry, and the processing circuitry, wherein a longest dimension ofthe case is less than twenty centimeters, and wherein a second-longestdimension of the case is less than ten centimeters.
 4. The radar systemof claim 1, further comprising an analog-to-digital converter configuredto generate digital signals based on the IF signals, wherein theprocessing circuitry is configured to detect the object based on thedigital signals.
 5. The radar system of claim 1, wherein the radarsystem is configured to operate in only one frequency band.
 6. The radarsystem of claim 1, further comprising: a local oscillator (LO); and acoupler configured to: deliver the RF signals to a transmit antenna; anddeliver the RF signals to the LO, wherein the LO is configured todeliver an LO signal to the receiver circuitry based on the RF signals.7. The radar system of claim 1, further comprising: a printed circuitboard (PCB), wherein the PLL circuitry, the processing circuitry, theVCO circuitry, and the receiver circuitry are mounted on the PCB; alocal oscillator (LO) mounted on the PCB and configured to: generate anLO signal; and deliver the LO signal to the receiver circuitry; and acoupler on the PCB configured to couple the RF signals to the LO,wherein the LO is configured to generate the LO signal based on thecoupled RF signals.
 8. The radar system of claim 1, wherein the receivercircuitry comprises: a mixer configured to generate two IF signals basedon the returned RF signals and a local oscillator signal; two IFamplifiers configured to filter the two IF signals into filtered IFsignals; and an analog-to-digital converter configured to generatedigital signals based on the filtered IF signals, wherein the processingcircuitry is configured to detect the object based on the digitalsignals.
 9. The radar system of claim 1, wherein the processingcircuitry is configured to drive the PLL circuitry to operate in acontinuous wave mode.
 10. The radar system of claim 1, wherein theprocessing circuitry is configured to detect a velocity of the objectbased on the IF signals.
 11. The radar system of claim 1, furthercomprising a crystal oscillator configured to operate as a master clockfor the processing circuitry and the PLL circuitry.
 12. The radar systemof claim 1, wherein the VCO circuitry is further configured to generatea divided RF signal, and wherein the PLL circuitry is further configuredto: generate a multiplied signal by multiplying a frequency of thereference signal; and compare the multiplied signal and the divided RFsignal, wherein the PLL circuitry is configured to generate the controlvoltage signal based on comparing the multiplied signal and the dividedRF signal.
 13. The radar system of claim 1, wherein the radar system isconfigured to mount on a vehicle, and wherein the processing circuitryis further configured to determine an estimated altitude of the vehiclebased on the IF signals.
 14. The radar system of claim 1, wherein theradar system is configured to mount on a vehicle, and wherein theprocessing circuitry is further configured to: determine at least tworeceive beams of the returned RF signals; and measure Doppler shift ofthe at least two receive beams, wherein the processing circuitry isconfigured to determine an estimated velocity of the vehicle based onthe Doppler shift of the at least two receive beams.
 15. A methodcomprising: driving phase-locked loop (PLL) circuitry to generate acontrol voltage signal; generating, at voltage-controlled oscillator(VCO) circuitry, radio-frequency (RF) signals based on the controlvoltage signal; transmitting, at one or more antennas, the RF signals;receiving, at the one or more antennas, returned RF signals; generating,at receiver circuitry, intermediate-frequency (IF) signals based on thereturned RF signals; and detecting an object based on the IF signals.16. The method of claim 15, wherein receiving the returned RF signalscomprises receiving, at four quadrants of receive antennas, the returnedRF signals, wherein generating IF signals comprises generating, at fourmixers, the IF signals, wherein the method further comprises filtering,at four IF amplifiers, IF signals into filtered IF signals, and whereindetecting the object is further based on the filtered IF signals. 17.The method of claim 15, wherein transmitting the RF signals comprisestransmitting, at the one or more antennas, the RF signals in only onefrequency band.
 18. The method of claim 15, wherein detecting the objectcomprises detecting a velocity of the object based on the IF signals.19. A radar system comprising: phase-locked loop (PLL) circuitryconfigured to generate a control voltage signal; processing circuitryconfigured to drive the PLL circuitry to generate the control voltagesignal; voltage-controlled oscillator (VCO) circuitry configured togenerate radio-frequency (RF) signals in a continuous wave mode based onthe control voltage signal; one or more transmit antennas configured totransmit the RF signals; a local oscillator (LO) configured to generatean LO signal based on the RF signals; a coupler configured to deliverthe RF signals to the one or more transmit antennas and to the LO; fourquadrants of receive antennas configured to receive returned RF signals;four mixers configured to generate intermediate-frequency (IF) signalsbased on the returned RF signals and based on the LO signal; four IFamplifiers configured to filter the IF signals; and fouranalog-to-digital converters configured to generate digital signalsbased on the filtered IF signals, wherein the processing circuitry isfurther configured to detect an object based on the digital signals. 20.The radar system of claim 19, further comprising a memory device,wherein the processing circuitry is configured to detect the object byat least: determining a location of the object based on the returned RFsignals; and determining a velocity of the object based on the returnedRF signals, wherein the processing circuitry is further configured to:store the location of the object to the memory device; and store thevelocity of the object to the memory device.